Method for screen printing solder paste onto a substrate with device premounted thereon

Abstract

A printing screen for screen printing fabrication substances such as solder paste has an aperture formed therein so that the screen may be placed on a substrate surface with a pre-mounted device extending through the aperture. A metal cap is bonded to the screen over the pre-mounted device to protect the device against damage during a subsequent screen printing operation. Different elements may, therefore, be bonded to a substrate in completely independent steps without the need for fluxing operations in later bonding operations.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A method of manufacturing electrical circuit devices of the type including a substrate having at least two elements solder-bonded to a common surface thereof comprising the successive steps of: (a) screening a solder-flux mixture onto a first area of the substrate surface;   (b) placing a first element on the screened-on solder-flux mixture;   (c) fusing the solder-flux mixture to bond the first element to the substrate;   (d) screening a solder-flux mixture onto a second area of the substrate surface by means of a screen having a covered aperture generally conforming with the first element;   (e) placing a second element on the screened-on solder-flux mixture on the second area; and   (f) heating the combination of substance, bonded first element, second element, and latter solder-flux mixture to fuse the latter solder-flux mixture and thereby bond the second element to the substrate.   
     
     
       2. A method as defined in claim 1 wherein the first element is a flip chip, the second element is a different element, and the solder-flux mixtures are of different compositions.